Method of transmitting scheduling request in mobile communication system and terminal apparatus for the same

ABSTRACT

A method and apparatus are provided for transmitting an uplink scheduling request in a mobile communication system. Scheduling request transmission cycles are set according to priorities between a terminal and a radio resource controlling node. The terminal transmits the scheduling request to the radio resource controlling node according to a scheduling request transmission cycle corresponding to a highest priority among priorities corresponding to uplink data or uplink control signals, if the uplink data or the uplink control signals are generated from an upper layer. The terminal receives scheduling information from the radio resource controlling node, and determines whether resource allocation information is included in the scheduling information. The terminal cyclically transmits the scheduling request to the radio resource controlling node in the scheduling request transmission cycle, if the resource allocation information is not included in the scheduling information.

PRIORITY

This application is a Continuation Application of U.S. patentapplication Ser. No. 13/546,504, filed on Jul. 11, 2012, which is aContinuation Application of U.S. Pat. No. 8,243,660, filed on Jun. 21,2007, which claims priority under 35 U.S.C. 10§119(a) to an applicationentitled “Method of Transmitting Scheduling Request in MobileCommunication System and Terminal Apparatus for the Same” filed in theKorean Industrial Property Office on Jun. 22, 2006 and assigned SerialNo. 2006-0056414, the contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for transmittingan uplink scheduling request in a mobile communication system.

2. Description of the Related Art

A multiplexing scheme employed in wireless communication may be dividedinto a time division multiplexing scheme, a code division multiplexingscheme, an orthogonal frequency division multiplexing scheme and soforth. A multiplexing scheme in most general use today is the codedivision multiplexing scheme, which is in turn divided into asynchronous scheme and an asynchronous scheme. However, the codedivision multiplexing scheme suffers from lack of resources because itbasically uses codes and thus orthogonal codes are insufficient.Thereupon, the Orthogonal Frequency Division Multiplexing (hereinafterOFDM) scheme is now in the spotlight.

The OFDM scheme, one of data transmission schemes using a multi-carrier,is a type of Multi-Carrier Modulation (hereinafter MCM) scheme in whicha serial input symbol stream is converted into parallel symbolsub-streams, the converted symbol sub-streams are modulated withmultiple sub-carriers (i.e., multiple sub-carrier channels) orthogonalto each other, and then the modulated symbol sub-streams aretransmitted. The OFDM scheme is similar to a Frequency DivisionMultiplexing (hereinafter FDM) scheme, but is different from the FDMscheme in that orthogonality between multiple sub-carriers is maintainedduring transmission, and frequency spectrums are overlappingly used.Thus, the OFDM scheme is efficient in the use of frequencies, is robustto frequency selective fading and multi-path fading, and can reduce theeffect of inter-symbol interference (hereinafter referred to as “ISI”)by using a guard interval. Further, the OFDM scheme can provide optimaltransmission efficient in high-speed data transmission because it makesit possible to simply design the structure of an equalizer in hardwareand has an advantage of high resistance to impulse noise.

The 3GPP (3^(rd) Generation Partnership Project) is currently discussinga next generation mobile communication system as a substitute for theUniversal Mobile Telecommunication Service (hereinafter UMTS) systemthat is the 3^(rd) generation mobile communication standard. Such a nextgeneration mobile communication system is called a Long Term Evolution(hereinafter LTE) system.

FIGS. 1A and 1B illustrate an example of a UMTS-based wireless mobilecommunication system, that is, a 3GPP LTE system, to which reference ismade in the present invention.

Referring to FIG. 1A, a user equipment (hereinafter referred to as “UE”)11 is a terminal for the 3GPP LTE system, and an Evolved Radio AccessNetwork (hereinafter E-RAN) 14 is a radio base station equipmentdirectly involved in communication with a terminal in an existing 3GPPsystem. The E-RAN 14 serves not only as a node B for managing cells, butalso as a Radio Network Controller (hereinafter RNC) for controlling aplurality of node Bs and radio resources. With regard to this, the E-RAN14 may include an Evolved Node B (hereinafter E-NB) 12 and an EvolvedRNC (hereinafter E-RNC) 13 that are physically separated into differentnodes, as in an existing 3GPP system, or integrated into one node. Byway of example, it is assumed herein that the E-NB 12 and the E-RNC 13are physically integrated into one node. However, it is obvious that thepresent invention can be applied in the same manner even if the E-RNC 13is physically separated from the E-NB 12.

An Evolved Core Network (hereinafter E-CN) 15 is a node into whichfunctions of a Serving GPRS Support Node (hereinafter SGSN) and aGateway GPRS Support Node (hereinafter GGSN) in an existing 3GPP systemare combined. The E-CN 15 is located between a Packet Data Network(hereinafter PDN) and the E-RAN 14, and serves as a gateway forallocating an Internet Protocol (hereinafter IP) address to the UE 11and connecting the UE 11 with the PDN 16. Since definitions andfunctions of the SGSN and the GGSN follow the standards specified in3GPP, a detailed description thereof will be omitted herein.

Referring to FIG. 1B, an Evolved UMTS Radio Access Network (hereinafterE-RAN) 110 has a simplified two node structure of an Evolved Node B(hereinafter E-NB) 120, 122, 124, 126, 128 and an anchor node 130, 132.A User Equipment (hereinafter UE or terminal) 101 is connected with anIP network via the E-RAN 110. Each E-NB 120 to 128 corresponds to anexisting Node B of the UMTS system, and is connected with the UE 101over a radio channel. Dissimilar to the existing Node B, the E-NB 120 to128 performs more complex functions. In the LTE system, since all usertraffics including a real-time service through an IP, such as a Voiceover IP (hereinafter VoIP) service, are serviced via a shared channel,an apparatus for collecting and scheduling situation information of UEsis needed. The E-NB 120 to 128 performs the function of such anapparatus.

In general, one E-NB controls a plurality of cells, and AdaptiveModulation & Coding (hereinafter AMC) for determining a modulationscheme and a channel coding rate in conformity with the channel state ofa UE is performed in an E-NB. Further, similar to High Speed DownlinkPacket Access (hereinafter HSDPA) or High Speed Uplink Packet Access orHSUPA; also called Enhanced-uplink Dedicated Channel or E-DCH of theUMTS system, the LTE system uses Hybrid Automatic Retransmission Request(hereinafter HARQ) between the E-NB 120 to 128 and the UE 101. However,since various Quality of Service (hereinafter QoS) requirements cannotbe satisfied by the HARQ alone, an upper layer may perform a separateARQ (hereinafter outer-ARQ), which also takes place between the UE 101and the E-NB 120 to 128. The HARQ refers to a technique for increasing areception success rate by soft-combining retransmitted data withpreviously received data without discarding the previously receiveddata, and is used for improving transmission efficiency in high-speedpacket communication, such as the HSDPA. In order to enable atransmission speed of maximum 100 Mbps, the LTE system is expected toemploy the OFDM scheme as radio access technology with a bandwidth of 20MHz.

FIG. 2 illustrates a procedure in which a UE transmits a schedulingrequest or buffer status report to an E-NB, based on 3GPP HSUPAtechnology.

If data or control signals to be transmitted by a UE is generated whenno resource is allocated to the UE, the UE transmits a schedulingrequest or buffer status report to an E-NB in order to request the E-NBto allocate radio resources for transmitting the data or controlsignals.

The scheduling request and buffer status report are different only inname, and are substantially the same. That is, they correspond to aprocedure for informing the E-NB of information on the priorities ofdata or control signals to be transmitted, the amounts of the data orcontrol signals according to priorities, filled in a buffer, etc. inorder to request the E-NB to allocate radio resources for transmittingthe data or control signals in uplink. Upon receiving the schedulingrequest or buffer status report from the UE, the E-NB allocates radioresources to the UE. In the present invention, the scheduling request isabbreviated as “SR”, and the buffer status report is abbreviated as“BSR”. The SR or BSR may be transmitted by PHY (PHYsical) signaling orMAC (Medium Access Control) signaling.

Referring to FIG. 2, if data or control signals to be transmitted aregenerated in each of UE#1, UE#2, . . . , and UE#N 201, 202, 203 by anupper layer, each of the UE#1, the UE#2, . . . , and the UE#N 201, 202,203 transmits an SR/BSR 231, 232, 233 to an E-NB 211. Upon receiving theSR/BSRs 231, 232, 233 from the UEs, the E-NB 211 generally allocatesradio resources to each of the UE#1, the UE#2, . . . , and the UE#N 201,202, 203 when a cell is not loaded with radio resources. The radioresources allocated to each of the UE#1, the UE#2, . . . , and the UE#N201, 202, 203 are determined by information included in the SR/BSR 231,232, 233 transmitted from each of the UEs, that is, the correspondingpriorities of the data or control signals to be transmitted and theamounts of the data or control signals according to priorities, filledin a buffer.

In FIG. 2, requested radio resources cannot be allocated to all of theUEs because a cell is loaded with radio resources, as designated byreference numeral 221. If the E-NB 211 receives the SR/BSRs 231, 232,233, but cannot allocate radio resources to all of the UE#1, the UE#2, .. . , and the UE#N 201, 202, 203, IDs of the UEs and radio resourceallocation information are not included in scheduling informationtransmitted in the downlink. If the UEs 201, 202, 203 cannot beallocated with radio resources for uplink transmission from thescheduling information transmitted in the downlink after transmittingthe SR/BSRs 231, 232, 233, they retransmit SR/BSRs 241, 242, 243 to theE-NB 211. This is performed on the assumption that the E-NB 211 fails toreceive the SR/BSRs 231, 232, 233 transmitted by the UEs. However, at apoint of time when the UEs retransmit the SR/BSRs 241, 242, 243 aftertransmitting the SR/BSRs 231, 232, 233, information on the priorities ofthe data or control signals to be transmitted by the UEs and the amountsof the data or control signals according to priorities, filled in abuffer, may vary, and thus the SR/BSRs 241, 242, 243 may includedifferent values from those in the SR/BSRs 231, 232, 233.

Although the E-NB 211 receives the SR/BSRs 241, 242, 243, it may notallocate radio resources for uplink transmission, requested by the UE#1,the UE#2, . . . , and the UE#N 201, 202, 203, because a cell is loadedwith radio resources, as the time when the E-NB 211 receives the SR/BSRs231, 232, 233. If IDs of the UEs and radio resource allocationinformation are not included in scheduling information transmitted indownlink after the SR/BSRs 241, 242, 243 are transmitted, the UEs canknow that radio resources for uplink transmission are not allocated.

If the UE#1, the UE#2, . . . , and the UE#N 201, 202, 203 cannot beallocated with requested radio resources for uplink transmission aftertransmitting the SR/BSRs 241, 242, 243, they retransmit SR/BSRs 251,252, 253 to the E-NB 211. If the E-NB 211 does not allocate radioresources to the UEs even after receiving the SR/BSRs 251, 252, 253, theUEs 201, 202, 203 retransmit SR/BSRs 261, 262, 263 to the E-NB 211. Thatis, if the UEs cannot be allocated with radio resources for uplinktransmission after transmitting SR/BSRs, they repeatedly retransmit theSR/BSRs. However, when the E-NB 211 does not allocate radio resourcesfor uplink transmission to the UEs not because it fails to receive theSR/BSRs, but because a cell is loaded with radio resources irrespectiveof successful reception of the SR/BSRs, not only the repetitive SR/BSRs241, 242, 243, 251, 252, 253, 261, 262, 263 are of no use, but also manyproblems, including inefficient consumption of radio resources and powerconsumption of UEs, and unnecessary interference may be caused.

SUMMARY OF THE INVENTION

The present invention has been made to address at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present inventionprovides a method and apparatus for preventing useless SR/BSRretransmission from terminals within a cell, which may occur when aradio resource controlling node successfully receives SR/BSRs from theterminals, and yet cannot allocate corresponding radio resources to allof the terminals.

In accordance with an aspect of the present invention, a method isprovided for transmitting an uplink scheduling request in a mobilecommunication system. Scheduling request transmission cycles are setaccording to priorities between a terminal and a radio resourcecontrolling node. The terminal transmits the scheduling request to theradio resource controlling node according to a scheduling requesttransmission cycle corresponding to a highest priority among prioritiescorresponding to uplink data or uplink control signals to therebyrequest the radio resource controlling node to allocate radio resourcesfor transmitting the uplink data or the uplink control signals, if theuplink data or the uplink control signals are generated from an upperlayer. The terminal receives scheduling information from the radioresource controlling node over a resource grant channel, and determineswhether resource allocation information is included in the schedulinginformation. The terminal cyclically transmits the scheduling request tothe radio resource controlling node in the scheduling requesttransmission cycle corresponding to the highest priority among thepriorities corresponding to the uplink data or the uplink controlsignals, if the resource allocation information is not included in thescheduling information.

In accordance with another aspect of the present invention, a terminalapparatus is provided having a buffer manager unit for storing uplinkdata or uplink control signals, which are transferred from an upperlayer, in a buffer, and controlling a scheduling request to betransmitted to a radio resource controlling node according to a statusof the buffer to thereby request the radio resource controlling node toallocate radio resources. The terminal apparatus also includes atransceiver unit for transmitting or retransmitting the schedulingrequest to the radio resource controlling node according to a schedulingrequest transmission cycle corresponding to a highest priority amongpriorities corresponding to the uplink data or the uplink controlsignals, and receiving scheduling information from the radio resourcecontrolling node over a resource allocation channel after transmittingthe scheduling request. The terminal apparatus further includes a timerfor acquiring transmission cycle information for the scheduling requestaccording to the priorities from the radio resource controlling nodethrough the transceiver unit, and controlling the transceiver unit tocyclically transmit and retransmit the scheduling request in thetransmission cycle corresponding to the highest priority, included inthe transmission cycle information when the resource allocationinformation is not included in the scheduling information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIGS. 1A and 1B illustrate an example of a mobile communication systemto which reference is made in the present invention;

FIG. 2 illustrates a procedure of retransmitting an SR/BSR in a statewhere a cell is loaded with radio resources;

FIG. 3 illustrates a method for efficiently controlling theretransmission of an SR/BSR in a state where a cell is loaded with radioresources in accordance with a first embodiment of the presentinvention;

FIGS. 4A and 4B illustrate the operation of a terminal in accordancewith the first embodiment of the present invention;

FIG. 5 illustrate the operation of a radio access network in accordancewith the first embodiment of the present invention;

FIG. 6 illustrates the structure of a terminal in accordance with thefirst embodiment of the present invention;

FIG. 7 illustrates the structure of a radio access network in accordancewith the first embodiment of the present invention;

FIG. 8 illustrates a method for efficiently controlling theretransmission of an SR/BSR in a state where a cell is loaded with radioresources in accordance with a second embodiment of the presentinvention;

FIG. 9 illustrates the operation of a terminal in accordance with thesecond embodiment of the present invention;

FIG. 10 illustrates the operation of a radio access network inaccordance with the second embodiment of the present invention;

FIG. 11 illustrates the structure of a terminal in accordance with thesecond embodiment of the present invention; and

FIG. 12 illustrates the structure of a radio access network inaccordance with the second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Embodiments of the present invention are described in detail withreference to the accompanying drawings. The same or similar componentsmay be designated by the same or similar reference numerals althoughthey are illustrated in different drawings. Also, in the followingdescription, a detailed description of known functions andconfigurations incorporated herein will be omitted for the sake ofclarity and conciseness. Further, it should be noted that only partsessential for understanding the operations according to the presentinvention will be described and a description of parts other than theessential parts will also be omitted for the sake of conciseness.

According to a first embodiment of the present invention, in order toprevent SR/BSRs from being unnecessarily transmitted or retransmitted,an E-NB notifies UEs of the lowest priority in the downlink. The lowestpriority refers to the lowest one of priorities included in SR/BSRs forwhich radio resources have been successfully allocated from amongSR/BSRs received by the E-NB. When each of the UEs transmits orretransmits an SR/BSR, it compares the lowest priority with the highestpriority among priorities included in the SR/BSR to be transmitted orretransmitted, and determines whether to transmit or retransmit theSR/BSR based on the comparison result. That is, the E-NB optimizesSR/BSR transmission/retransmission by prohibiting useless SR/BSRtransmission or retransmission.

FIG. 3 illustrates a method of transmitting/retransmitting an SR/BSRaccording to the first embodiment of the present invention.

Referring to FIG. 3, if data or control signals to be transmitted inuplink are generated in a UE 301 by an upper layer and transferred to atransmission buffer, the UE 301 transmits an SR/BSR 321 to an E-NB 311in order to request the E-NB 311 to allocate radio resources fortransmitting the data or control signals. The SR/BSR 321 includesinformation on service priorities according to radio bearers,corresponding to such information as the data or control signals and theamounts of the data or control signals. If data and control signals aretransferred together to the transmission buffer or data corresponding todifferent applications is transferred together to the transmissionbuffer, a plurality of priorities mapped to the respective data orcontrol signals may be included in the SR/BSR. In this case, the SR/BSRincludes information on the amounts of the data or control signalsaccording to priorities starting from the highest priority. In FIG. 3,it is assumed that the highest priority included in the SR/BSR 321 is“X”.

Next, the E-NB 311 transmits a notification 331 on the lowest priority,that is, a criterion for permitting SR/BSR transmission, in downlink toUEs within a cell. As an example, the lowest priority for permittingSR/BSR transmission may be set in consideration of (Radio ResourceManagement (hereinafter RRM) and the lowest one of priorities includedin SR/BSRs for which radio resources have been successfully allocatedfrom among SR/BSRs that the E-NB 311 has previously received from UEswithin a corresponding cell. For example, when numerous radio resourcesremain, SR/BSRs from all UEs can be permitted by setting the lowestpriority for permitting SR/BSR transmission, which is notified to theUEs, to 1 (or 0) although the lowest priority for radio resourceallocation in a previous TTI is 6.

The lowest priority for permitting SR/BSR transmission (hereinafterlowest permissible priority), which is transmitted through thenotification 331, allows UEs within a cell to control SR/BSRtransmission.

That is, the UE 301 compares the lowest permissible priority included inthe notification 331 with the highest priority among service prioritiescorresponding to the data or control signals transferred to thetransmission buffer by the upper layer, which are included in the SR orBSR to be transmitted. If a result of the comparison shows that thehighest priority among the service priorities is lower than the lowestpermissible priority, the UE 301 does not retransmit the SR/BSR becausethe E-NB 311 will not allocate radio resources even if the UE 301retransmits the SR/BSR. In contrast, if the highest priority is equal toor higher than the lowest permissible priority, the UE 301 retransmitsthe SR/BSR. The lowest priority may be cyclically transmitted over acommon channel. As an example, it is assumed herein that the lowestpriority, together with scheduling information (hereinafter SI) forinforming UEs within a cell of radio resource allocation information foruplink transmission, is transmitted in every sub-frame (here, thesub-frame is a minimum unit for allocating radio resources for uplinktransmission to a UE, and radio resource allocation information foruplink transmission may be transmitted to the UE in every sub-frame)over a common channel. However, the present invention does not exclude ascheme in which the lowest priority is cyclically or non-cyclicallytransmitted over a dedicated channel allocated to each UE, rather than acommon channel. In FIG. 3, it is assumed that the lowest permissiblepriority included in the notification 331 is “Y”.

If the UE 301 transmits the SR/BSR 321 to the E-NB 311, but the E-NB 311does not allocate radio resources for uplink transmission to the UE 301,the UE 301 compares the lowest permissible priority Y, recently notifiedby the E-NB 311, with the highest priority X included in the SR/BSR 321to be transmitted, as designated by reference numeral 341. If X is lessthan Y (X<Y), then the UE 301 does not retransmit the SR/BSR.

Reference numeral 332 indicated that the lowest priority for permittingSR/BSR transmission is cyclically transmitted by the E-NB 311, andreference numeral 342 indicates that the UE 301 receives the cyclicallytransmitted lowest priority Y and compares it with the highest priorityincluded in an SR/BSR to be transmitted.

In FIG. 3, the lowest permissible priority is continuously transmittedfrom the E-NB 311 to the UE 301 through notifications 332 to 351.Meanwhile, the 301 does not retransmit the SR/BSR because thetransmitted lowest priority Y is still higher than the highest priorityX of the SR/BSR.

However, if the lowest permissible priority is changed from Y to Z dueto a change in a cell load status, the UE 301 compares the highestpriority X of the SI/BSR to be transmitted with the changed lowestpermissible priority Z, as designated by reference numeral 361.

If a result of the comparison shows that X is equal to or greater thanZ, the UE 301 retransmits the SR/BSR 371 to the E-NB 301. The E-NB 311allocates radio resources for uplink transmission to the UE 301 andtransmits the SI in downlink by using information included in the SR/BSR371, as designated by reference numeral 372.

Further, when radio bearer setup or reconfiguration is performed so asto receive a specific service, the E-NB sets a MAC logical channelpriority for a logical channel corresponding the specific service insuch a manner as to match with the service, and informs the UE of theset MAC logical channel priority, thereby enabling prioritysynchronization between the E-NB and the UE.

In FIG. 3, when data or control signals are generated by an upper layer,and thus an SR/BSR is required to be transmitted in order to requestuplink resource allocation, a UE is permitted to initially transmit theSR/BSR, but can retransmit the SR/BSR when the highest priority of theSR/BSR is equal to or greater than the lowest priority for permittingSR/BSR transmission, which is notified in downlink by an E-NB. In otherwords, when the E-NB does not allocate radio resources for correspondinguplink transmission to the UE (i.e., the ID of the UE and radio resourceallocation information are not included in SI received from the E-NB)after the initial transmission of the SR/BSR, and thus the UE needs toretransmit the SR/BSR, only an SR/BSR including the highest priorityequal to or greater than the lowest priority notified by the E-NB can beretransmitted.

Although not illustrated in FIG. 3, the lowest priority for permittingSR/BSR transmission, which is notified in downlink by the E-NB, may beapplied to from an initial SR/BSR. That is, whether to transmit aninitial SR/BSR may be determined by first determining whether thehighest priority included in the initial SR/BSR is equal to or higherthan the lowest priority.

Further, although not illustrated in FIG. 3, a permissible UE/user classlevel or a permissible service data rate may be used in thenotifications 331, 332 and 351, instead of using the lowest priority forpermitting SR/BSR transmission. In this case, an SR/BSR is transmittedonly when the class level of a UE or user transmitting the SR/BSR isequal to or higher than a permissible UE/user class level, and is nottransmitted when the class level of the UE or user is lower than thepermissible UE/user class level. In a similar manner, an SR/BSR istransmitted only when a target service data rate of the SR/BSR is equalto or lower than a permissible service data rate, and is not transmittedwhen the target service data rate is higher than the permissible servicedata rate. Further, service priorities included in the SR/BSR may beused in combination with the permissible UE/user class level and thepermissible service data rate, for example.

FIGS. 4A and 4B illustrate the operation of a UE according to the firstembodiment of the present invention. Of these two drawings, FIG. 4Arelates to a method of controlling SR/BSR retransmission by the lowestpriority without controlling initial SR/BSR transmission, and FIG. 4Brelates to a method of SR/BSR retransmission as well as initial SR/BSRtransmission by the lowest priority.

Referring to FIG. 4A, if data or control signals to be transmitted in anuplink are generated by an upper layer and transferred to a transmissionbuffer in step 401, and thus the UE is required to transmit an SR/BSR,the UE transmits an initial SR/BSR to an E-NB in step 402, and receivesa resource grant channel from the E-NB in step 403. SI is transmittedover the resource grant channel, and UEs within a cell can know throughthe SI which radio resources are allocated to which UEs.

In step 411, the UE, which has transmitted the SR/BSR, determineswhether radio resource allocation information for the UE's uplinktransmission is included in the SI received over the resource grantchannel. If the radio resource allocation information is included in theSI, the UE proceeds to step 421, and transmits the data or controlsignals in the transmission buffer by using allocated radio resources.However, if the radio resource allocation information for the UEs uplinktransmission is not included in the SI received over the resource grantchannel, the UE proceeds to step 422, and acquires the lowest priorityfor permitting SR/BSR transmission, which is cyclically transmitted indownlink.

In step 431, the UE determines whether the highest priority included inthe SR/BSR transmitted in step 402 is lower than the lowest priority forpermitting SR/BSR transmission, received in step 422.

If a result shows that the highest priority included in the SR/BSR islower than the lowest priority for permitting SR/BSR transmission, theUE returns to step 403, and receives the resource grant channel.However, if the highest priority is not lower than the lowest priority,the UE proceeds to step 442, retransmits the SR/BSR and then returns tostep 403.

Referring to FIG. 4B, if data or control signals to be transmitted in anuplink are generated by an upper layer and transferred to a transmissionbuffer in step 451, and thus the UE is required to transmit an SR/BSR,in step 452, the UE acquires the lowest priority for permitting SR/BSRtransmission, which is cyclically transmitted in downlink from an E-NB.In step 461, the UE compares the highest priority included in the SR/BSRtransmitted in step 451 with the lowest priority for permitting SR/BSRtransmission, acquired in step 452.

If a result of the comparison shows that the highest priority includedin the SR/BSR is lower than the lowest priority for permitting SR/BSRtransmission, the UE returns to step 451. However, if the highestpriority is not lower than the lowest priority, the UE proceeds to step472, transmits (or retransmits) the SR/BSR and then receives a resourcegrant channel in step 473.

In step 481, the UE, which has transmitted the SR/BSR in step 472,determines whether radio resource allocation information for the UE'suplink transmission is included in the resource grant channel receivedin step 473. If a result shows that the radio resource allocationinformation is included in the resource grant channel, the UE proceedsto step 491, and transmits the data or control signals in thetransmission buffer by using allocated radio resources. However, if theradio resource allocation information is not included in the resourcegrant channel, the UE returns to step 452.

FIG. 5 illustrates the operation of an E-NB according to the firstembodiment of the present invention.

Referring to FIG. 5, if a cycle in which the lowest priority forpermitting SR/BSR transmission is transmitted arrives in step 501, thenin step 511, the E-NB sets the lowest priority for permitting SR/BSRtransmission by considering the lowest one of priorities included inSR/BSRs for which radio resources have been successfully allocated fromamong SR/BSRs that the E-NB has already received from UEs within a cell,RRM for managing a cell load status, and other factors. In step 521, theE-NB transmits the lowest priority for permitting SR/BSR transmission,set in step 511, in a downlink at a set time by using a set channel.

FIG. 6 illustrates the structure of a UE according to the firstembodiment of the present invention.

Referring to FIG. 6, the UE includes an upper layer 601, adata/signaling buffer manager unit 611, a transceiver unit 621, anSR/BSR transmission (retransmission) determiner unit 631 and a timer641. The upper layer 601 includes both an upper control unit forgenerating control signals and an upper application unit for generatingdata.

Data or control signals generated in the upper layer 601 are transferredto a transmission buffer (not shown). If the transmission buffer isfilled with the data or control signals transferred from the upper layer601, the data/signaling buffer manager unit 611 transmits an SR/BSR toan E-NB through the transceiver unit 621 in order to request the E-NB toallocate radio resources for uplink transmission. Using a resource grantchannel signal received in the downlink through the transceiver unit 621after transmitting the SR/BSR, the UE determines whether radio resourcesfor the UE's uplink transmission are allocated. If the radio resourcesfor the UE's uplink transmission are allocated, the UE transmits thedata or control signals in the transmission buffer by using theallocated radio resources. However, if the radio resources for the UE'suplink transmission are not allocated, the SR/BSR transmissiondeterminer unit 631 determines whether to retransmit the SR/BSR, basedon the lowest priority for permitting SR/BSR transmission, which isreceived in the downlink through the transceiver unit 621. According tothe determination, the SR/BSR transmission determiner unit 631retransmits the SR/BSR or continues to receive a resource grant channeland the lowest priority for permitting SR/BSR transmission, which iscyclically transmitted in the downlink. As described in connection withFIG. 3, the SR/BSR transmission determiner unit 631 determines toretransmit the SR/BSR only when the highest priority included in theSR/BSR to be retransmitted is equal to or higher than the lowestpriority for permitting SR/BSR transmission, received in the downlink.The timer 641 determines a cycle in which the lowest priority forpermitting SR/BSR transmission is transmitted.

Although not illustrated in FIG. 3, when even initial SR/BSRtransmission is controlled using the lowest priority for permittingSR/BSR transmission, as already described, the lowest priority forpermitting SR/BSR transmission is received in downlink through thetransceiver unit 621 before an initial SR/BSR is transmitted, and theSR/BSR transmission determiner unit 631 uses the received lowestpriority for determining whether to transmit the initial SR/BSR.Further, based on the determination, the transceiver unit 621 transmitsthe initial SR/BSR or does not retransmit the SR/BSR and continues toreceive the lowest priority for permitting SR/BSR transmission, which iscyclically transmitted.

FIG. 7 illustrates the structure of an E-NB according to the firstembodiment of the present invention.

Referring to FIG. 7, the E-NB according to this embodiment includes atimer 701, a transceiver unit 721 and a lowest priority determiner unit711.

The timer 701 determines a cycle in which the lowest priority forpermitting SR/BSR transmission is transmitted in the downlink. Thelowest priority determiner unit 711 sets the lowest priority forpermitting SR/BSR transmission by considering the lowest one ofpriorities included in SR/BSRs for which radio resources have beensuccessfully allocated from among SR/BSRs that the E-NB has alreadyreceived from UEs within a cell or a cell load status. The transceiverunit 721 cyclically transmits the lowest priority for permitting SR/BSRtransmission, set by the lowest priority determiner unit 711, in thedownlink to UEs over a corresponding channel.

In the aforementioned first embodiment of the present invention, thelowest priority notified in the downlink to a UE is compared with thehighest priority included in an SR/BSR, but a UE/user class level or thedata rate of a service to be requested may be compared with apermissible UE/user class level or a permissible service data rate.

In a second embodiment of the present invention, retransmission timersaccording to priorities are defined. If requested radio resources arenot allocated after an SR/BSR is initially transmitted, the SR/BSR isretransmitted after the elapse of a time set by a retransmission timercorresponding to the highest priority among priorities included in theSR/BSR to be retransmitted. In this manner, an SR/BSR with a lowerpriority is transmitted relatively less frequently than an SR/BSR with ahigher priority, so that SR/BSR retransmission can be optimized.

FIG. 8 illustrates a procedure of retransmitting an SR/BSR according tothe second embodiment of the present invention.

Referring to FIG. 8, as designated by reference numeral 821, a UE 801within a cell acquires cycle (timer) information for SR/BSRretransmission, which is defined according to priorities. The cycleinformation may be transmitted through system information broadcastedwithin the cell, transmitted UE by UE through signaling, or prearrangedbetween the UE 801 and an E-NB 811 by an implicit rule. If the cycleinformation is prearranged by an implicit rule, this may be implementedas hard coding within the UE. Although the present invention is notlimited to a specific scheme, it is assumed in FIG. 8 that the UE 801acquires the cycle information through system information.

If data or control signals to be transmitted in the uplink are generatedin the UE 801 by an upper layer and transferred to a transmissionbuffer, the UE 801 transmits an SR/BSR 831 to the E-NB 811, and starts acycle (timer) corresponding to the highest priority included in theSR/BSR 831 by using the acquired cycle information according topriorities. That is, assuming in FIG. 8 that the highest priorityincluded in the SR/BSR 831 is “X”, a cycle (timer) corresponding to X isstarted.

If the UE 801 receives a resource grant channel after transmitting theSR/BSR 831, but cannot be allocated with radio resources for the UE 801through SI received during the SR/BSR retransmission cycle correspondingto the highest priority X, it retransmits the SR/BSR when theretransmission cycle (timer) expires, and restarts the retransmissiontimer, as designated by reference numeral 832. If the UE 801 cannot beallocated with radio resources even during the second retransmissioncycle, it retransmits the SR/BSR when the restarted timer expires, asdesignated by reference numeral 833. That is, if radio resources for theUE 801 are not allocated, the UE 801 performs retransmission accordingto the cycle information corresponding to the highest priority includedin the SR/BSR.

The retransmission cycle may be differently set according to priorities.That is, a longer retransmission cycle is set for an SR/BSR with arelatively low priority so that the SR/BSR is transmitted lessfrequently, and a shorter retransmission cycle is set for an SR/BSR witha relatively high priority so that the SR/BSR is transmitted morefrequently. In this manner, SR/BSR retransmission can be optimized.

Although not illustrated in FIG. 8, it is also possible to start theretransmission cycle (timer) corresponding to the highest priority X notwhen the UE 831 transmits the SR/BSR, but when the UE 801 determinesthat it receives the resource grant channel but cannot be allocated withradio resources for the UE 801 through the SI.

Further, the highest priority included in the SR/BSR may be changed inthe process of SR/BSR retransmission, and subsequently the UE 801retransmits the SR/BSR according to a retransmission cycle correspondingto the changed highest priority.

FIG. 9 illustrates the operation of a UE according to the secondembodiment of the present invention.

Referring to FIG. 9, if data or control signals to be transmitted in theuplink are generated by an upper layer and transferred to a transmissionbuffer in step 901, and thus the UE detects a need for SR/BSRtransmission, the UE transmits an SR/BSR to an E-NB in step 902.Further, using SR/BSR retransmission cycle (timer) information accordingto priorities, which has been already acquired through systeminformation or signaling according to UEs, the UE starts aretransmission cycle (timer) corresponding to the highest priorityincluded in the SR/BSR transmitted in step 902.

Next, the UE receives a resource grant channel in step 903. In step 911,using SI included in the received resource grant channel, the UEdetermines whether radio resources for the UE are allocated. If radioresources for the UE are allocated, the UE proceeds to step 921, andtransmits the data or control signals in the transmission buffer byusing the allocated radio resources. However, if radio resources for theUE are not allocated, the UE proceeds to step 931, and determineswhether the cycle (timer) started in step 902 expires. If the cycle(timer) does not expire, the UE returns to step 903. However, if thecycle (timer) expires, the UE proceeds to step 941, and retransmits theSR/BSR, starts a retransmission cycle (timer) corresponding to thehighest priority included in the retransmitted SR/BSR and then returnsto step 903.

FIG. 10 illustrates the operation of an E-NB according to the secondembodiment of the present invention.

Referring to FIG. 10, in step 1001, the E-NB detects that it is time totransmit SR/BSR retransmission cycle (timer) information according topriorities through system information or detects a need for transmittingthe information through signaling according to UEs. In step 1011, theE-NB sets the SR/BSR retransmission cycle (timer) information accordingto priorities by considering such information as a radio resource status(e.g., cell load status) and SR/BSRs received from UEs within a cell. Instep 1021, the E-NB transmits the SR/BSR retransmission cycle (timer)information according to priorities to UEs through system information orsignaling according to UEs.

FIG. 11 illustrates the structure of a UE according to the secondembodiment of the present invention.

Referring to FIG. 11, the UE includes an upper layer 1101, adata/signaling buffer manager unit 1111, a transceiver unit 1121 and atimer 1131.

The upper layer 1101 includes both an upper control unit for generatingcontrol signals and an upper application unit for generating data. Dataor control signals generated in the upper layer 1101 are transferred toa transmission buffer (not shown). If the transmission buffer is filledwith the data or control signals transferred from the upper layer 1101,the data/signaling buffer manager unit 1111 transmits an SR/BSR to anE-NB through the transceiver unit 1121 in order to request the E-NB toallocate radio resources for uplink transmission. Using SR/BSRretransmission cycle (timer) information according to priorities, whichhas been already acquired through signaling according to UEs, the timer1131 starts a retransmission cycle (timer) corresponding to the highestpriority included in the SR/BSR transmitted by the UE. According to aresource grant channel signal received in the downlink through thetransceiver unit 1121 after transmitting the SR/BSR, the UE determineswhether radio resources for the UE's uplink transmission are allocated.If the radio resources for the UE's uplink transmission are allocated,the UE transmits the data or control signals in the transmission bufferthrough the transceiver unit 1121 by using the allocated radioresources. However, if the radio resources for the UE's uplinktransmission are not allocated, the UE determines whether the previouslystarted cycle (timer) expires. If the cycle (timer) expires, the UEretransmits the SR/BSR through the transceiver unit 1121, and starts acycle (timer) corresponding to the highest priority included in theretransmitted SR/BSR.

FIG. 12 illustrates the structure of an E-NB according to the secondembodiment of the present invention.

Referring to FIG. 12, the E-NB includes a priority-by-prioritycycle/timer setting unit 1201, a transceiver unit 1211 and a timer 1221.

The priority-by-priority cycle/timer setting unit 1201 sets SR/BSRretransmission cycles (timers) according to priorities. That is, thepriority-by-priority cycle/timer setting unit 1201 sets a correspondingretransmission cycle (timer) on a priority-by-priority basis byconsidering such information as a radio resource status (e.g., cell loadstatus) and SR/BSRs received from UEs within a cell. The transceiverunit 1211 of the E-NB transmits the set retransmission cycle (timer)according to each priority to a corresponding UE through systeminformation or signaling according to UEs. If the retransmission cycle(timer) set on a priority-by-priority basis is transmitted throughsystem information, the system information may be cyclically transmittedaccording to the settings of the timer 1221.

The aforementioned first and second embodiments of the present inventionmay be performed simultaneously rather than separately. For example,SR/BSR retransmission can be repeatedly and cyclically performedaccording to retransmission cycles according to priorities by applyingthe first embodiment of the present invention when the highest prioritytransmitted to an E-NB by a UE is lower than the lowest permissiblepriority received from the E-NB, and simultaneously applying the firstand second embodiments of the present invention when the highestpriority is equal to or higher than the lowest permissible priority.

As describe above, the present invention can effectively preventterminals from unnecessarily retransmitting SR/BSRs, which may be causedwhen a radio resource controlling node successfully receives SR/BSRsfrom the terminals, and yet cannot allocate corresponding radioresources to all of the terminals.

While the invention has been shown and described with reference tocertain embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedby the appended claims.

What is claimed is:
 1. A method of transmitting an uplink scheduling request in a mobile communication system, the method comprising the steps of: setting scheduling request transmission cycles according to priorities between a terminal and a radio resource controlling node; transmitting, by the terminal, the scheduling request to the radio resource controlling node according to a scheduling request transmission cycle corresponding to a highest priority among priorities corresponding to uplink data or uplink control signals to thereby request the radio resource controlling node to allocate radio resources for transmitting the uplink data or the uplink control signals, if the uplink data or the uplink control signals are generated from an upper layer; receiving, by the terminal, scheduling information from the radio resource controlling node over a resource grant channel, and determining whether resource allocation information is included in the scheduling information; and cyclically retransmitting, by the terminal, the scheduling request to the radio resource controlling node in the scheduling request transmission cycle corresponding to the highest priority among the priorities corresponding to the uplink data or the uplink control signals, if the resource allocation information is not included in the scheduling information.
 2. The method as claimed in claim 1, wherein setting the scheduling request transmission cycles comprises acquiring scheduling request transmission cycle information through system information received from the radio resource controlling node.
 3. The method as claimed in claim 1, wherein setting the scheduling request transmission cycles further comprises setting scheduling request transmission cycle information by an implicit rule between the radio resource controlling node and the terminal.
 4. The method as claimed in claim 1, wherein the priorities are service priorities according to radio bearers corresponding to the uplink data or the uplink control signals or according to a priorities channel for the uplink data or the uplink control signals.
 5. A terminal apparatus comprising: a buffer manager unit for storing uplink data or uplink control signals, which are transferred from an upper layer, in a buffer, and controlling a scheduling request to be transmitted to a radio resource controlling node according to a status of the buffer to thereby request the radio resource controlling node to allocate radio resources; a transceiver unit for transmitting or retransmitting the scheduling request to the radio resource controlling node according to a scheduling request transmission cycle corresponding to a highest priority among priorities corresponding to the uplink data or the uplink control signals, and receiving scheduling information from the radio resource controlling node over a resource allocation channel after transmitting the scheduling request; and a timer for acquiring transmission cycle information for the scheduling request according to the priorities from the radio resource controlling node through the transceiver unit, and controlling the transceiver unit to cyclically transmit and retransmit the scheduling request in the transmission cycle corresponding to the highest priority, included in the transmission cycle information when the resource allocation information is not included in the scheduling information.
 6. The terminal apparatus as claimed in claim 5, wherein the transceiver unit acquires the transmission cycle information through system information received from the radio resource controlling node.
 7. The terminal apparatus as claimed in claim 5, wherein the priorities are service priorities according to radio bearers corresponding to the uplink data or the uplink control signals or according to a priorities channel for the uplink data or the uplink control signals. 